Ophthalmic lenses, dioptric formulae for combined cylindrical lenses : the prism-dioptry, and other optical papers (1900)
Prentice, Charles Frederick, b. 1854 · Philadelphia : Keystone · leaf 32
H^ for the frontsurface c^ is slightly closer to the face of the lens than the focal line l^F^lfor the back surface c-. Aside from this, in making a bi-cylindrical lens itis difficult to insure the chief planes of refraction being strictly at right-angles to each other, so that failure in this is… … Fig. 21.Double or Bi-cylindrical Lens. lens ma} generally be accepted as a vanishing quantity in proportion tothe focal distance, we may consider a common focal point to exist for bothrefractino- surfaces.
Lenses
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